Next ISS Crew Incompatible
RobertB-DC writes "The International Space Station's replacement crew is being pulled for the B-Team. While the Reuters story quotes officials talking about "certain considerations", a Moscow Times article lays it on the line: '"Incompatible" ISS Crew Ditched' due to 'a psychological incompatibility.' The Russian-American team had already been shaken up once, when the original American member dropped out due to illness. Now, they're being replaced with a whole new pair."
The dynamics of a two-person crew are harder to manage than those of the three-person crew. If the two have a bad argument, there's no third party to mediate, and you end up with each one calling Earth looking for someone to back him up. In the end, both end up feeling isolated. With a three-person crew, there's someone to mediate and serve as a safety valve - even if two of the crew members aren't speaking to each other, there's a third person there they can talk to.